Background: Idiopathic pulmonary fibrosis (IPF) is form of interstitial lung disease which generally occurs in persons 60 years and older.It is characterised by a high symptom burden, and frequent encounters with health services. This study aimed to determine the economic burden of IPF in Australia with a focus on resource utilisation and associated direct costs.

Methods: Participants were recruited from the Australian IPF Registry (AIPFR) between August 2018 and December 2019. Data on resource utilisation and costs were collected via cost diaries and linked administrative data. Clinical data were collected from the AIPFR. Costing was performed from a partial societal perspective and a "bottom up" costing methodology was utilized focusing on direct medical and non-medical costs. Costs were standardized to 2021 Australian dollars ($).

Results: The average annual total direct costs per person with IPF was $31,655 (95% confidence interval: $27,723-$35,757). Extrapolating costs based on prevalence estimates, the total annual costs in Australia are projected to be $299 million (95% confidence interval: $262 million -$338 million) which is based on published prevalence for IPF. Costs were mainly driven by antifibrotic medication, hospital admissions and medications for comorbidities. Disease severity, comorbidities and antifibrotic medication all had varying impacts on resource utilisation and costs.

Conclusions: This study provides the first comprehensive analysis of IPF-related direct costs in Australia, identifies the key cost drivers and provides a framework for future health economic analyses. Additionally, it provided insight into the major cost drivers which include antifibrotic medication, hospital admissions and medications related to comorbidities. Our findings emphasise the importance of the appropriate management of comorbidities in the care of people with IPF as this was one of the main reasons for hospitalisations.